1. Field of Invention
This invention relates in general to bearings and, in particular, to cylindrical type squeeze bearing systems.
2. Description of the Prior Art
The general theory underlying the operating principle of squeeze-type bearings is well documented in the prior art. The article entitled "Compressible Squeeze Films and Squeeze Bearings" by E. O. Salbu in the June 6, 1964 issue of the Transaction of the ASME Journal of Basic Engineering is an excellent basic reference for an understanding of the squeeze bearing technology. Since that time, various bearing systems have been suggested which rely on the basic squeeze bearing principle.
Recently, tubular or cylindrical squeeze bearings have been suggested as the bearing elements for the magnetic transducer carriage assembly of the transducer positioning system of a disk file. The function of these positioning systems is to position a magnetic transducer to a particular track on a magnetic disk. The positioning operation involves linear movement of the head over a range of travel of about one to two inches, with very precise accuracy. The transducer is mounted on a head-arm that is generally attached to the movable coil of a voice coil actuator. The coil and head-arm are attached to a carriage assembly which functions to precisely guide the head and coil as they are moved along a linear path between track addresses. It is important that the head to disk spacing be controlled since the spacing is critical to the successful writing and reading of data on to the disk. It is also important that the recording gap of the magnetic head assume the same angle, e.g., 90.degree., to the center line of the track if data is to be written and read accurately.
Conventional ball bearing roller systems that have been associated with carriage and way assembly disk file positioning systems operate satisfactorily but have one major disadvantage. That is that they inherently have a static friction problem and variable dynamic friction. These problems adversely affect access time and transducer positioning accuracy in the disk file. Since cylindrical squeeze bearings do not have these problems, their potential has created considerable interest in the use of these bearings for disk file applications.
Copending PCT application Ser. No. US82/01828, filed Dec. 30, 1982, entitled "Improved Long Tube Bender Element Squeeze Bearing", and assigned to the assignee of the present invention and commonly assigned application Ser. No. 273,280, filed June 12, 1981, in the name of Scranton and entitled "Planar and Cylindrical Oscillating Pneumatodynamic Bearings" disclose cylindrical squeeze bearings for disk file actuators.
As shown and described in these applications, the bearing system comprises generally a pair of cylindrical bearing elements disposed coaxially in a nested relationship. One bearing element is provided with the piezoelectric transducer or driving element to cause it to vibrate, that is, change its cross-sectional shape, the transducer being physically attached to one of the bearing elements. It will be appreciated by those persons skilled in the art that the dimensional tolerances of the piezoelectric transducer and the cylindrical bearing element to which it must be physically attached are critical to the proper operation of the bearing system. The requirement of these critical tolerances between the transducer and the driven bearing element substantially increases the cost of the bearing.
The present invention minimizes the need for critical tolerances which is inherent when the cross-section of the driving element is dictated by the configuration of the bearing element and may not be a shape that lends itself to being readily and inexpensively manufactured.